Enhanced oil recovery (EOR) has become a significant industry practice in the last twenty years. Of all the known EOR techniques, CO2 injection is more popular due to high displacement efficiency of CO2. Unfortunately even when in a supercritical state, CO2 has a low viscosity and suffers from poor conformance, mobility, and ultimately low sweep efficiency. One method that has been developed to alleviate this problem is the use of surfactants to emulsify the supercritical CO2 in water (brine) as an emulsion. This creates an apparent viscosity in the CO2 and improves the mobility and conformance of the CO2 as it propagates through the strata in an oil field.
Although much work has been done to determine the best surfactants and injection strategies, little has been published on how to implement supercritical CO2 surfactant foam solutions. Several key problems arise in the economical implementation of these techniques. For instance, one method of implementing this solution is to utilize a CO2 soluble surfactant injected directly into the CO2 line. Most CO2 injection lines are maintained at 1500-2500 psi and have variable rates of flow. A complex high-pressure pump and delivery system is needed to accommodate these variables. Further given that these surfactants are generally added on an alternating cycle, the system is only utilized for short amounts of time on a given well. This adds to the complexity of the operation, and is also an inefficient, i.e. a costly, application of equipment.
Some examples of prior processes and machines include WO 2008081048 which describes a system for another form of enhanced oil recovery, alkaline surfactant polymer (ASP) flooding. A new grinding apparatus for improving the dissolution time of the polymer is provided. WO 2008071808 describes an entire system for implementing an ASP solution in the field. WO 2007011812 describes a mobile unit for another method of EOR by nitrogen flooding. The unit is comprised of a nitrogen generating unit and a pumping system that can deliver the generated nitrogen to the wellbore. Further it teaches the pumping of other well fluids concurrently with the nitrogen. US2004/034521 describes a three in one nitrogen, chemical, coiled tubing system on a mobile unit. U.S. Pat. No. 6,702,011 describes a mobile unit for delivery of nitrogen through coiled tubing.
Thus there is a need for a mobile technology which enables the injection of surfactant at a controlled concentration into a high pressure stream of liquid or supercritical CO2.